Ultrahigh productivity photobioreactors for algal biofuel production

Algal biodiesel is a biodegradable and sustainable alternative to traditional petroleum fuels. Algal biodiesel is synthesised from algal lipids via transesterification and has many desirable physical properties for fuel use. Current photobioreactors are inefficient. This thesis looks to increase efficiency and reduce energetic running costs. This was undertaken by the design, construction and trialling of an LED photobioreactor. The controlled growth of the algae, specifically Chlorella emersonii, using pulsed monochromatic or bi-chromatic light conditions with comparison to continuous white light to improve light economy is explored in this thesis. The prediction of biodiesel profile from the growth conditions is also investigated for Chlorella emersonii. Chapter 1 is a general introduction to the area of algal biodiesel. This introductory chapter reviews the current literature regarding microalgae growth conditions and control, processing microalgae to produce biodiesel and photobioreactor designs for the controlled growth of algae. The known effects of different light sources and types on algal growth are also reviewed. Chapter 2 concerns the pulsing-LED vertical airlift photobioreactor design, construction and testing, including an overview of the system constructed and the process of design to combat specific issues. Results from the testing of the photobioreactor are reported in this chapter which include analysis of the resultant fatty acid methyl ester (FAME) profile of algae grown under various pulsed mono-chromatic and bi-chromatic light conditions and the comparison to continuous white light. This chapter draws together the hypotheses and stand-alone observations reported in the current literature allowing direct comparisons for different light conditions and conclusions to be reported which include the effect on resultant FAME profile and not just lipid percentage. Chapter 3 explores the effect of environmental factors on the fatty acid methyl ester composition of the algal biodiesel. This chapter describes the effect of carbon dioxide, nitrate, phosphate and iron levels, length of culture and the effect of supplementary carbon sources on Chlorella emersonii growth and resultant FAME composition. The result of synergetic effects of nutrient levels and length of algal cultivation are analysed in addition to the stage of algal growth and its impact on FAME profile. Chapter 4 details the procedures used for the growth of algae, the production of the algal biodiesel and the development of techniques used for analysis of the resultant biodiesel. The techniques and conditions employed for the growth of the algae as well as the extraction and transesterification of the algal lipids are explained.